1. Field of the Invention
The present invention relates to an active vibration control system for use in a motor-assisted hybrid vehicle having a generator motor integrally combined with an engine serving as a propulsive source for propelling the hybrid vehicle, the generator motor being used, when operating in a motor mode, as an assistive propulsive source for assisting the output power of the engine.
2. Description of the Related Art
Generally, engines on vehicles operate by converting the power of the intermittent explosions in the cylinders to the rotation of the crankshaft (output shaft) and outputting the rotary torque of the crankshaft. Therefore, the rotary torque inevitably fluctuates in synchronism with the intermittent explosions. There has been proposed a torque fluctuation suppressing apparatus for suppressing the rotary torque fluctuations by detecting an increase in the rotary torque generated by the crankshaft, supplying a field current to a generator motor that is coupled to the crankshaft in torque transmitting and receiving relation thereto, and applying an inverse torque from the generator motor to the crankshaft when the rotary torque generated by the crankshaft increases. For details, reference should be made to Japanese Patent Publication No. 4-24538 and Japanese Laid-Open Patent Publication No. 61-135936.
The conventional torque fluctuation suppressing apparatus generates the inverse torque by controlling the generator motor in a feed-forward control mode based on engine rotational speed fluctuations detected by a crankangle sensor. Therefore, if the engine ignition timing varies due to a change in the intake temperature, then the torque fluctuation suppressing apparatus fails to perform its control process properly and tends to lower its vibration reducing performance.
The conventional torque fluctuation suppressing apparatus determines vibration control data at the time the accelerator pedal is depressed to a certain depth for a constant throttle valve opening. Consequently, when the accelerator pedal is depressed to a different depth to change the throttle valve opening, the vibration control capability of the torque fluctuation suppressing apparatus is greatly lowered.